diff --git a/source/tanya/encoding/ascii.d b/source/tanya/encoding/ascii.d
new file mode 100644
index 0000000..ba272da
--- /dev/null
+++ b/source/tanya/encoding/ascii.d
@@ -0,0 +1,501 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Functions operating on ASCII characters.
+ *
+ * ASCII is $(B A)merican $(B S)tandard $(B C)ode for $(B I)nformation
+ * $(B I)nterchange.
+ *
+ * Copyright: Eugene Wissner 2017.
+ * License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
+ *                  Mozilla Public License, v. 2.0).
+ * Authors: $(LINK2 mailto:info@caraus.de, Eugene Wissner)
+ * Source: $(LINK2 https://github.com/caraus-ecms/tanya/blob/master/source/tanya/encoding/ascii.d,
+ *                 tanya/encoding/ascii.d)
+ */
+module tanya.encoding.ascii;
+
+import tanya.meta.trait;
+
+const string fullHexDigits = "0123456789ABCDEFabcdef"; /// 0..9A..Fa..f.
+const string hexDigits = "0123456789ABCDEF"; /// 0..9A..F.
+const string lowerHexDigits = "0123456789ABCDEF"; /// 0..9a..f.
+const string digits = "0123456789"; /// 0..9.
+const string octalDigits = "01234567"; /// 0..7.
+
+/// A..Za..z.
+const string letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+const string uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; /// A..Z.
+const string lowercase = "abcdefghijklmnopqrstuvwxyz"; /// a..z.
+
+/**
+ * Whitespace, Horizontal Tab (HT), Line Feed (LF), Carriage Return (CR),
+ * Vertical Tab (VT) or Form Feed (FF).
+ */
+const string whitespace = "\t\n\v\f\r ";
+
+/// Letter case specifier.
+enum LetterCase : bool
+{
+    upper, /// Uppercase.
+    lower, /// Lowercase.
+}
+
+/**
+ * Checks for an uppecase alphabetic character.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is an uppercase alphabetic
+ *          character, $(D_KEYWORD false) otherwise.
+ */
+bool isUpper(C)(C c)
+if (isSomeChar!C)
+{
+    return (c >= 'A') && (c <= 'Z');
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isUpper('A'));
+    assert(isUpper('Z'));
+    assert(isUpper('L'));
+    assert(!isUpper('a'));
+    assert(!isUpper('!'));
+}
+
+/**
+ * Checks for a lowercase alphabetic character.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a lowercase alphabetic
+ *          character, $(D_KEYWORD false) otherwise.
+ */
+bool isLower(C)(C c)
+if (isSomeChar!C)
+{
+    return (c >= 'a') && (c <= 'z');
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isLower('a'));
+    assert(isLower('z'));
+    assert(isLower('l'));
+    assert(!isLower('A'));
+    assert(!isLower('!'));
+}
+
+/**
+ * Checks for an alphabetic character (upper- or lowercase).
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is an alphabetic character,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isAlpha(C)(C c)
+if (isSomeChar!C)
+{
+    return isUpper(c) || isLower(c);
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isAlpha('A'));
+    assert(isAlpha('Z'));
+    assert(isAlpha('L'));
+    assert(isAlpha('a'));
+    assert(isAlpha('z'));
+    assert(isAlpha('l'));
+    assert(!isAlpha('!'));
+}
+
+/**
+ * Checks for a digit.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a digit,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isDigit(C)(C c)
+if (isSomeChar!C)
+{
+    return (c >= '0') && (c <= '9');
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isDigit('0'));
+    assert(isDigit('1'));
+    assert(isDigit('2'));
+    assert(isDigit('3'));
+    assert(isDigit('4'));
+    assert(isDigit('5'));
+    assert(isDigit('6'));
+    assert(isDigit('7'));
+    assert(isDigit('8'));
+    assert(isDigit('9'));
+    assert(!isDigit('a'));
+    assert(!isDigit('!'));
+}
+
+/**
+ * Checks for an alphabetic character (upper- or lowercase) or a digit.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is an alphabetic character or a
+ *          digit, $(D_KEYWORD false) otherwise.
+ */
+bool isAlphaNum(C)(C c)
+if (isSomeChar!C)
+{
+    return isAlpha(c) || isDigit(c);
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isAlphaNum('0'));
+    assert(isAlphaNum('1'));
+    assert(isAlphaNum('9'));
+    assert(isAlphaNum('A'));
+    assert(isAlphaNum('Z'));
+    assert(isAlphaNum('L'));
+    assert(isAlphaNum('a'));
+    assert(isAlphaNum('z'));
+    assert(isAlphaNum('l'));
+    assert(!isAlphaNum('!'));
+}
+
+/**
+ * Checks for a 7-bit ASCII character.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is an ASCII character,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isASCII(C)(C c)
+if (isSomeChar!C)
+{
+    return c < 128;
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isASCII('0'));
+    assert(isASCII('L'));
+    assert(isASCII('l'));
+    assert(isASCII('!'));
+    assert(!isASCII('©'));
+    assert(!isASCII('§'));
+    assert(!isASCII(char.init)); // 0xFF
+    assert(!isASCII(wchar.init)); // 0xFFFF
+    assert(!isASCII(dchar.init)); // 0xFFFF
+}
+
+/**
+ * Checks for a control character.
+ *
+ * Control characters are non-printable characters. Their ASCII codes are those
+ * between 0x00 (NUL) and 0x1f (US), and 0x7f (DEL).
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a control character,
+ *          $(D_KEYWORD false) otherwise.
+ *
+ * See_Also: $(D_PSYMBOL isPrintable),  $(D_PSYMBOL isGraphical).
+ */
+bool isControl(C)(C c)
+if (isSomeChar!C)
+{
+    return (c <= 0x1f) || (c == 0x7f);
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isControl('\t'));
+    assert(isControl('\0'));
+    assert(isControl('\u007f'));
+    assert(!isControl(' '));
+    assert(!isControl('a'));
+    assert(!isControl(char.init)); // 0xFF
+    assert(!isControl(wchar.init)); // 0xFFFF
+}
+
+/**
+ * Checks for a whitespace character.
+ *
+ * Whitespace characters are:
+ *
+ * $(UL
+ *  $(LI Whitespace)
+ *  $(LI Horizontal Tab (HT))
+ *  $(LI Line Feed (LF))
+ *  $(LI Carriage Return (CR))
+ *  $(LI Vertical Tab (VT))
+ *  $(LI Form Feed (FF))
+ * )
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a whitespace character,
+ *          $(D_KEYWORD false) otherwise.
+ *
+ * See_Also: $(D_PSYMBOL whitespace).
+ */
+bool isWhite(C)(C c)
+if (isSomeChar!C)
+{
+    return ((c >= 0x09) && (c <= 0x0d)) || (c == 0x20);
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isWhite('\t'));
+    assert(isWhite('\n'));
+    assert(isWhite('\v'));
+    assert(isWhite('\f'));
+    assert(isWhite('\r'));
+    assert(isWhite(' '));
+}
+
+/**
+ * Checks for a graphical character.
+ *
+ * Graphical characters are printable characters but whitespace characters.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a control character,
+ *          $(D_KEYWORD false) otherwise.
+ *
+ * See_Also: $(D_PSYMBOL isControl), $(D_PSYMBOL isWhite).
+ */
+bool isGraphical(C)(C c)
+if (isSomeChar!C)
+{
+    return (c > 0x20) && (c < 0x7f);
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isGraphical('a'));
+    assert(isGraphical('0'));
+    assert(!isGraphical('\u007f'));
+    assert(!isGraphical('§'));
+    assert(!isGraphical('\n'));
+    assert(!isGraphical(' '));
+}
+
+/**
+ * Checks for a printable character.
+ *
+ * This is the opposite of a control character.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a control character,
+ *          $(D_KEYWORD false) otherwise.
+ *
+ * See_Also: $(D_PSYMBOL isControl).
+ */
+bool isPrintable(C)(C c)
+if (isSomeChar!C)
+{
+    return (c >= 0x20) && (c < 0x7f);
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isPrintable('a'));
+    assert(isPrintable('0'));
+    assert(!isPrintable('\u007f'));
+    assert(!isPrintable('§'));
+    assert(!isPrintable('\n'));
+    assert(isPrintable(' '));
+}
+
+/**
+ * Checks for a hexadecimal digit.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a hexadecimal digit,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isHexDigit(C)(C c)
+if (isSomeChar!C)
+{
+    return ((c >= '0') && (c <= '9'))
+        || ((c >= 'a') && (c <= 'f'))
+        || ((c >= 'A') && (c <= 'F'));
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isHexDigit('0'));
+    assert(isHexDigit('1'));
+    assert(isHexDigit('8'));
+    assert(isHexDigit('9'));
+    assert(isHexDigit('A'));
+    assert(isHexDigit('F'));
+    assert(!isHexDigit('G'));
+    assert(isHexDigit('a'));
+    assert(isHexDigit('f'));
+    assert(!isHexDigit('g'));
+}
+
+/**
+ * Checks for an octal character.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is an octal character,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isOctalDigit(C)(C c)
+if (isSomeChar!C)
+{
+    return (c >= '0') && (c <= '7');
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isOctalDigit('0'));
+    assert(isOctalDigit('1'));
+    assert(isOctalDigit('2'));
+    assert(isOctalDigit('3'));
+    assert(isOctalDigit('4'));
+    assert(isOctalDigit('5'));
+    assert(isOctalDigit('6'));
+    assert(isOctalDigit('7'));
+    assert(!isOctalDigit('8'));
+}
+
+/**
+ * Checks for a octal character.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: $(D_KEYWORD true) if $(D_PARAM c) is a octal character,
+ *          $(D_KEYWORD false) otherwise.
+ */
+bool isPunctuation(C)(C c)
+if (isSomeChar!C)
+{
+    return ((c >= 0x21) && (c <= 0x2f))
+        || ((c >= 0x3a) && (c <= 0x40))
+        || ((c >= 0x5b) && (c <= 0x60))
+        || ((c >= 0x7b) && (c <= 0x7e));
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(isPunctuation('!'));
+    assert(isPunctuation(':'));
+    assert(isPunctuation('\\'));
+    assert(isPunctuation('|'));
+    assert(!isPunctuation('0'));
+    assert(!isPunctuation(' '));
+}
+
+/**
+ * Converts $(D_PARAM c) to uppercase.
+ *
+ * If $(D_PARAM c) is not a lowercase character, $(D_PARAM c) is returned
+ * unchanged.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: The lowercase of $(D_PARAM c) if available, just $(D_PARAM c)
+ *          otherwise.
+ */
+C toUpper(C)(const C c)
+if (isSomeChar!C)
+{
+    return isLower(c) ? (cast(C) (c - 32)) : c;
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(toUpper('a') == 'A');
+    assert(toUpper('A') == 'A');
+    assert(toUpper('!') == '!');
+}
+
+/**
+ * Converts $(D_PARAM c) to lowercase.
+ *
+ * If $(D_PARAM c) is not an uppercase character, $(D_PARAM c) is returned
+ * unchanged.
+ *
+ * Params:
+ *  C = Some character type.
+ *  c = Some character.
+ *
+ * Returns: The uppercase of $(D_PARAM c) if available, just $(D_PARAM c)
+ *          otherwise.
+ */
+C toLower(C)(const C c)
+if (isSomeChar!C)
+{
+    return isUpper(c) ? (cast(C) (c + 32)) : c;
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    assert(toLower('A') == 'a');
+    assert(toLower('a') == 'a');
+    assert(toLower('!') == '!');
+}
diff --git a/source/tanya/encoding/package.d b/source/tanya/encoding/package.d
new file mode 100644
index 0000000..b40aa50
--- /dev/null
+++ b/source/tanya/encoding/package.d
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * This package provides tools to work with text encodings.
+ *
+ * Copyright: Eugene Wissner 2017.
+ * License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
+ *                  Mozilla Public License, v. 2.0).
+ * Authors: $(LINK2 mailto:info@caraus.de, Eugene Wissner)
+ * Source: $(LINK2 https://github.com/caraus-ecms/tanya/blob/master/source/tanya/encoding/package.d,
+ *                 tanya/encoding/package.d)
+ */
+module tanya.encoding;
+
+public import tanya.encoding.ascii;
diff --git a/source/tanya/math/mp.d b/source/tanya/math/mp.d
index 5d0263f..70ae06b 100644
--- a/source/tanya/math/mp.d
+++ b/source/tanya/math/mp.d
@@ -15,9 +15,9 @@
 module tanya.math.mp;
 
 import std.algorithm;
-import std.ascii;
 import std.range;
 import tanya.container.array;
+import tanya.encoding.ascii;
 import tanya.memory;
 import tanya.meta.trait;
 import tanya.meta.transform;
diff --git a/source/tanya/net/uri.d b/source/tanya/net/uri.d
index 8dfa379..2be1978 100644
--- a/source/tanya/net/uri.d
+++ b/source/tanya/net/uri.d
@@ -14,8 +14,7 @@
  */
 module tanya.net.uri;
 
-import std.ascii : isAlphaNum, isDigit;
-import std.uni : isAlpha, isNumber;
+import tanya.encoding.ascii;
 import tanya.memory;
 
 /**
@@ -199,8 +198,8 @@ struct URL
                         this.pass = source[start + i + 1 .. pos]; 
                     }
                 }
-                else if (!c.isAlpha &&
-                         !c.isNumber &&
+                else if (!c.isAlpha() &&
+                         !c.isDigit() &&
                          c != '!' &&
                          c != ';' &&
                          c != '=' &&